Re: [PATCH 4/4] memcg: always enable kmemcg on the default hierarchy

[Vladimir Davydov <vdavydov@parallels.com>]

On Mon, Sep 07, 2015 at 11:39:06AM +0200, Michal Hocko wrote:
...
> > > I might be wrong here of course but if the default should be switched it
> > > would deserve a better justification with some numbers so that people
> > > can see the possible drawbacks.
> > 
> > Personally, I'd prefer to have it switched on by default, because it
> > would force people test it and report bugs and performance degradation.
> > If one finds it really crappy, he/she should be able to disable it.
> 
> I do not think this is the way of introducing new functionality. You do
> not want to force users to debug your code and go let it disable if it
> is too crappy.

One must first enable CONFIG_KMEM, which is off by default.

Anyway, we aren't talking about enabling it by default in the legacy
hierarchy, only in the unified hierarchy, which must be explicitly
enabled by passing __DEVEL__save_behavior. I think that's enough.

> 
> > > I agree that the per-cgroup knob is better than the global one. We
> > 
> > Not that sure :-/
> 
> Why?

I'm not sure there is use cases which need having kmem acct enabled in
one cgroup and disabled in another.

Thanks,
Vladimir

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